This invention relates to a one-way clutch to allow the transmission of a rotating torque between inner and outer rings only in one direction.
A typical prior art one-way clutch is disclosed in the Japanese Utility Model Laid-open Publication No. 64-49738 and shown in FIG. 5. This one-way clutch has an inner ring 21, an outer ring 22, a plurality of sprags 23 interposed between the inner ring 21 and the outer ring 22, retainers 24 for holding the sprags 23 in a manner allowing the sprags 23 to swing, a spring 25 for forcing the sprags 23 in one direction, end bearings 26 which are slidably fit to the outer ring 22 and support the retainers 24 to positionally fix them in an axial direction, and annular retainer plates 27 which support the end bearings 26 in the axial direction from outside with pawls 27a holding clamped portions 22a of the outer ring 22.
FIG. 6 shows a front view of the retainer plate 27 and FIG. 7 shows a side view of the retainer plate 27 taken in the direction of arrow VII of FIG. 6.
As shown in FIGS. 6 and 7, the retainer plates 27 are each formed from an annular thin plate such that one side of the plate has four recesses 27b radially extending with both ends opened at even intervals in an circumferential direction of the plate and the other side of the plate has also four recesses 27c radially extending with both ends opened at even intervals in the circumferential direction. Naturally, the phase of the recesses on each side is offset from the phase of the recesses on the other side, and each recess functions as a passage for lubrication. The retainer plates 27 are adapted to slide in contact with plastic washers 28 fixed to rotating members 29 such as gears.
However, in the prior art one-way clutch described above, a problem with warping of the retainer plates 27 caused by quenching, tempering and other heat processes during production occurs because the retainer plates 27 are formed from a thin plate such that the thin plate has alternate recesses as described above and that the configuration of the axial cross section of the retainer plates varies at different points in the circumferential direction. In addition, the retainer plates 27 do not have sufficient rigidity. Therefore, for example, the retainer plates 27 are easily bent, and the axial length of the pressure plates as indicated by T in FIG. 5 is easily reduced by elastic deformation when a sandwiching force is axially applied to the pressure plates from both sides.
FIG. 8 is a partial plan view schematically illustrating a contact state of the plastic washer 28 and the retainer plate 27. As shown in FIG. 8, each plastic washer has lubricant holding channels 28b formed at plural locations spaced apart in a circumferential direction on a face 28a opposing the retainer plate 27. Consequently, protruding portions 27d which are back side of the recesses 27b on the retainer plates 27 intermittently contact an angled portion A of each lubricant holding channel 28b during rotation of the plastic washers 28, thus causing the angled portions A to wear. The resulting abrasion debris can then cause the lubricant to deteriorate. Note that in FIG. 8, arrow R indicates a direction in which the plastic washers 28 rotate.